A new bound for t−wise almost universal hash functions

Using the pigeon-hole principle, we derive a new bound for the key length in a t-wise almost universal hash function where the multicollision or t-collision probability is bounded above by epsilon in the range [0,1]. The important features of this bound are (1) it decreases very slowly as t increases, and (2) the key length grows at least linearly with the logarithm of the message length. To our knowledge, this is the first almost universal hash bound for any integer t > 1. This work arises from the use of t-wise almost universal hash functions in manual authentication protocols

Rational authentication protocols

ABSTRACT We use ideas from game theory to improve two families of authentication protocols, namely password-based and manual authentication schemes. The protocols will be transformed so that even if an intruder attacks different protocol runs between honest nodes, its expected payoff will still be lower than when it does not attack. A rational intruder, who always tries to maximise its payoff, therefore has no incentive to attack any protocol run among trustworthy parties

Separating two roles of hashing in one-way message authentication

We analyse two new and related families of one-way authentication protocols, where a party wants to authenticate its public information to another. In the first, the objective is to do without shared passwords or a PKI, making use of low-bandwidth empirical/authentic channels where messages cannot be faked or modified. The analysis of these leads to a new security principle, termed separation of security concerns, under which protocols should be designed to tackle one-shot attacks and combinatorial search separately. This also leads us develop a new class of protocols for the case such as PKI where a relatively expensive signature mechanism exists. We demonstrate as part of this work that a popular protocol in the area, termed MANA I, neither optimises human effort nor offers as much security as had previously been believed. We offer a number of improved versions for MANA I that provides more security for half the empirical work, using a more general empirical channel

Authenticating ad hoc networks by comparison of short digests

We show how to design secure authentication protocols for a non-standard class of scenarios. In these authentication is not bootstrapped from a PKI, shared secrets or trusted third parties, but rather using a minimum of work by human user(s) implementing the low-band width unspoofable channels between them. We develop both pairwise and group protocols which are essentially optimal in human effort and, given that, computation. We compare our protocols with recent pairwise protocols proposed by, for example, Hoepman and Vaudenay. We introduce and analyse a new cryptographic primitive-a digest function-that is closely related to short-output universal hash functions. © 2007 Elsevier Inc. All rights reserved

A proof-of-proximity framework for device pairing in ubiquitous computing environments

Ad hoc interactions between devices over wireless networks in ubiquitous computing environments present a security problem: the generation of shared secrets to initialize secure communication over a medium that is inherently vulnerable to various attacks. However, these ad hoc scenarios also offer the potential for physical security of spaces and the use of protocols in which users must visibly demonstrate their presence and/or involvement to generate an association. As a consequence, recently secure device pairing has had significant attention from a wide community of academic as well as industrial researchers and a plethora of schemes and protocols have been proposed, which use various forms of out-of-band exchange to form an association between two unassociated devices. These protocols and schemes have different strengths and weaknesses – often in hardware requirements, strength against various attacks or usability in particular scenarios. From ordinary user‟s point of view, the problem then becomes which to choose or which is the best possible scheme in a particular scenario. We advocate that in a world of modern heterogeneous devices and requirements, there is a need for mechanisms that allow automated selection of the best protocols without requiring the user to have an in-depth knowledge of the minutiae of the underlying technologies. Towards this, the main argument forming the basis of this dissertation is that the integration of a discovery mechanism and several pairing schemes into a single system is more efficient from a usability point of view as well as security point of view in terms of dynamic choice of pairing schemes. In pursuit of this, we have proposed a generic system for secure device pairing by demonstration of physical proximity. Our main contribution is the design and prototype implementation of Proof-of-Proximity framework along with a novel Co- Location protocol. Other contributions include a detailed analysis of existing device pairing schemes, a simple device discovery mechanism, a protocol selection mechanism that is used to find out the best possible scheme to demonstrate the physical proximity of the devices according to the scenario, and a usability study of eight pairing schemes and the proposed system